Reversing linear solenoids are generally known and form the prior art. For example, bistable designs are used for driving electrical medium-voltage switching devices, with electrolytic capacitors being needed for the power supply of the magnets. Further fields of use can be found, for example, in solenoid valves which should be able to maintain a state against a returning force without any control current. In addition, there is a high number of further applications, inter alia in sorting and conveying plants, but also in the automotive sector (in particular transmission engineering, central locking systems, shift locks) as well as in knitting machines. Important possible areas of use are also present in the field of so-called hot-runner engineering (actuating the needles of injection molding tools) and in the field of robot welding tongs (tracking the welding electrode, with the required clearance compensation being able to be ensured by springs).
A disadvantage of known reversing linear solenoids, which frequently precludes their use instead of pneumatic or hydraulic drives (or spring accumulators locked by force transmission), is their frequently small electrical efficiency. This results in substantial costs in medium-voltage switching devices using (bistable) reversing linear solenoids, primarily due to the expensive electrolytic capacitors. In other fields of the art, in particular with valves in engines—for example gas valves in large gas engines—the small electrical efficiency results in an unwanted limitation of the permitted frequency or occurrence of switching by the power loss occurring in the coils (the coils would be thermally destroyed at higher switching frequencies).
A further disadvantage of known reversing linear solenoids is their small dynamics since, in particular with comparatively long-stroke drives (long-stroke in comparison with the magnet diameter), only a small initial force is frequently available and, in addition, comparatively large tolerances are unavoidable. For instance, power switches should disconnect short-circuits from the mains as fast as possible in switching off or should impact the zero crossing of the current or that of the voltage on switching on; high dynamics with short dead times are required for this purpose—this is only insufficiently possible using conventional reversing linear solenoids.
Finally, a disadvantage of known bistable reversing linear solenoids can be seen in the fact that they tend to show the highest armature speed when the armature reaches an end stroke position at the end of an adjustment procedure. This results in a high effort for the end position damping or restricts the service life of the magnet.
In some applications, above all in valves and electrical switching devices, reversing linear solenoids should be monostable instead of bistable optionally to be able to adopt a safe end position without any control current.
It is therefore the underlying object of the invention to increase the electrical efficiency of polarized reversing linear solenoids, in particular of polarized bistable reversing linear solenoids. The new magnets should furthermore be able to have dynamics which are high in comparison with known reversing linear solenoids with reduced dead times. In addition, a common demand on actuators is a compact construction.